Feedback arrangements for beam switching tubes



June 25, 1957 s. KUCHINSY ETAL 2,797,357

FEEDBACK ARRANGEMENTS FOR BEAM SWITCHING 3 Sheets-Sheet 1 Filed Jan. 22, 1954 INVENTO L KU SKY I L D AYERS AGENT Jun 25, 1957 S. KUCHINSY EI'AL FEEDBACK ARRANGEMENTS FOR BEAM SYSIITCl-IINGv TUBES I 3 Sheets-Sheet 3 Filed Jan. 22, l954 s [6 \H *zoov L 4 as -|oov X;

+ IOOV 9 mvamos SAUL KUCHINSKY EARL D. AYERS AGENT FEEDBAOK ARRANGEh/ENTS FOR BEAM SWITCHING TUBES Saul Kuchinsky, Phoenixville, Pa., and Earl D. Ayers, Cranbury, N. 3., assignors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Application January 22, 1%4, Serial No. 405,602

13 Claims. (Cl. 31521) This invention relates to electron tubes and particularly to magnetron type multiple position beam switching tubes and circuits for the operation of the same.

An example of the general type of multiple beam switching tube with which this invention is concerned is illustrated in Figs. 3 and 7 of Saul Kuchinskys paper entitled, Multiple Output Beam Switching Tubes for Computers in General-Purpose Use, which was presented at the 1953 National Convention of the Institute of Radio Engineers. The tube shown in those figures has, Within an evacuated envelope, an elongated indirectly heated thermionic cathode which is surrounded by three hollow cylindrical arrays of electrodes. The array of electrodes which is next adjacent to the cathode is composed of 10 beam forming and directing electrodes which are normally called spade electrodes.

The individual spade electrodes, or simply spades, are coextensive in length with the electron emissive portion of the cathode, have a U or trough-shaped transverse cross sectional configuration, and are spaced substantially equi-distant one from another to form the cylindrical array. The array which is next adjacent to the spade electrodes is a sleeve-like hollow cylindrical anode electrode which has slots running longitudinally thereof. These slots are equal in number to the number of spade electrodes in the spade array, and each slot is aligned with the space between two adjacent spade electrodes and also with respect to the cathode.

The outer array of electrodes comprises a plurality of individual plate-like target or electron receiving electrodes spaced one from another to form a hollow cylindrical array. The target electrodes are aligned with the slots in the sleeve-like anode in such a manner that electrons passing through the slots in the anode will.

impinge one of the target electrodes. Leads to the various spades, targets, anode, and cathode are brought through the tube base.

The tube is normally surrounded by a permanent magnet which provides a magnetic field permeating the tube and having lines of force which are substantially parallel to the longitudinal axis of the cathode. Normally, under the condition where no input signal is applied to the tube, each of the spades is maintained at a positive potential with respect to the cathode through an individual spade impedance which includes a resistive element which is connected from a source of positive potential. Likewise, the anode electrode is connected through a source of positive potential which may be, but not necessarily is, the source of potential to which the spades are connected. Each individual target electrode is connected to a source of positive potential through an individual target impedance which includes a resistive element. Under these so-called static conditions, the magnetic and electrostatic fields existing within the tube are so balanced with respect to one another that electrons emitted from the cathode travel in curved paths around the cathode and subsequently very few of these electrons impinge upon States atent O ice the outer electrodes of the tube. If, however, the potential on one of the spades is changed so that the spade is at or near the potential of the cathode, the relationship between the electrostatic field and the magnetic field is changed in the area of the spade having the lowered potential and an electron beam is formed between the cathode and an edge of the spade having the lowered potential. The edge of the spade to which the beam will be attracted is known as the leading edge and is determined by the direction in which the magnetic field tends to rotate the beam. This direction can be determined by the polarity of the magnetic field. When the electron beam impinges on the spade having the lowered potential, electron flow takes place through the spade impedance, causing a potential drop across the resistive element of the spade impedance. If the value of the resistive element is properly chosen, the voltage drop across the spade impedance will be sufiicient to maintain the spade at or near to the cathode potential. Thus, the electron beam will remain locked in on that spade even though the means previously mentioned for lowering the spade potential is no longer utilized for that period.

Since only a small part of the electrons in the beam are utilized to lock in the beam on the spade, other electrons of the beam pass through the aperture in the sleevelike anode which is adjacent to the spade and impinges on the target electrode, causing an electron flow through the target resistor. The voltage drop across the target resistor is utilized as the output signal of the tube. The electron beam may be switched from one spade to another in any of several ways. One way, which is often used, is to momentarily reduce the potential on the sleevelike anode, causing the beam to fan out or spread and thus impingev one the next adjacent spade. When electrons impinge on the next adjacent spade, the current through the spade resistor of that spade causes a potential drop across that resistor, thus lowering the spade voltage and attracting more electrons to the spade. When the spade potential has lowered to its critical value, that is, at or near the cathode potential, the beam switches to the adjacent electrode and locks in on that electrode. Since the time required for the beam to switch from one spade to another is known, the anode potential should be lowered only for that amount of time. If the anode is maintained at a lowered potential for a greater period of time, the beam will advance for more than one beam position. The term beam position normally includes a spade, the target on which electrons impinge when the electron beam is locked in on the spade, and one or more switching electrodes which may be used to cause the electron beam to switch to the next position.

For a more detailed description of the operation of these and similar tubes, reference is made to U. S. Patent 2,764,711 issued Sept. 25, 1956, to Saul Kuchinsky, and U. S. Patent 2,721,955 issued Oct. 25, 1955, to S. P. Fan and Saul Kuchinsky. The various tubes in these applications are also suitable for use with the present invention.

For example, in the tube shown in Figures 7 and 8 of the Fan-Kuchinsky patent, an array of rod-like switching grids replaces the sleeve-like anode which has been described as being disposed between the spades and the target electrodes. One of the rod-like switching electrodes is disposed between the lagging edge of each spade and a target electrode. Pulses of small amplitudes may be applied to these switching grids in order to control the advancement of the electron beam in the switching tubes.

While these tubes perform in a very satisfactory manner, the number of spades which may be included within the arrays has been somewhat restricted, due to the fact that when the spades become too small, the lowering of the spade potential on the small spade does not cause a sufficient change in the electrostatic field configuration to cause an electron beam to be formed. Thus, for practical purposes if the diameter of these tubes is to remain small, a practical limit of the number of spades, and thus, the number of beam positions, may be 15, for example. It is true that tubes having more beam positions may be made by scaling up existing designs for these tubes, but other considerations indicate that this course is not too desirable. For instance, scaled up tubes would require a larger magnet to provide the strong magnetic field which is necessary for the reliable operation of the tube and higher voltages would be required on various electrodes. The larger magnet would add bulk and cost to the tube, and the higher voltage requirements would add bulk and cost in the form of more exacting and more complicated power supplies. Since these beam switching tubes are to be used in installations where compactness is almost essential, such as in aircraft equipment and in large computers where many of these tubes may be employed, the disadvantage of in creased physical size of the scaled up tubes should not be minimized.

In addition, the switching time of these tubes is dependent upon the R-C time constant of the spade circuit. In the existing tubes it has been found that spade resistors of the order of 100,000 ohms are required to produce sufiicient potential drop to lower the spade potential to, at, or near the cathode potential. Thus, the high value of the spade impedance or, more accurately termed, the spade resistance, limits the upper switching speed of the tube.

Further, in order to enable the beam switching tube to drive terminal equipment without additional intermediate amplifiers, an increase in power output of the switching tubes is desirable.

A principal object of the present invention is to provide an improved magnetron type multiple beam switching tube.

Another object of the present invention is to provide an improved, more reliable magnetron type multiple beam switching tube which has a larger number of beam positions per unit tube diameter than heretofore obtainable.

A further object of the present invention is to provide an improved magnetron type multiple position beam switching tube which is capable of switching from one beam position to another at higher speeds than have been previously obtainable.

Yet another object of the present invention is to provide an improved magnetron type multiple position beam switching tube which is reliable in operation and which has a larger power output than similar prior art tubes.

In accordance with the present invention, a multiple beam switching tube is provided with means for utilizing the output signal from one beam position to maintain one or more previous spades at a lower potential. Thus, even though each individual spade is of such small size that its own eifect on the electrostatic field is such that no electron beam would be formed when the spade potential is lowered to, at, or near the cathode potential, the combined effect of two or more spades at a lowered potential is utilized to insure that an electron beam will be formed and will lock in on the leading edge of the most advanced spade.

In addition, because of the increased change in the electrostatic field, the peak spade current is materially greater (from three to five, or even seven times greater) than is the case with a similar tube where the beam is formed as a result of only one spade having a lowered potential. In view of this increased spade current, the spade load resistor value may be decreased, since a much smaller value will suffice to produce a voltage drop suflicient to lower the spade at, or near the cathode potential. With a reduction in the spade resistor value, the R-C constant of the spade circuit is reduced and consequently the beam switching time from one position to another is reduced. The increase in spade current is a result of increased beam current, so an increase in output current is also achieved.

Another benefit which accrues as a result of having more than one spade lowered in potential while the beam is at each beam position is that the width of the electron beam is decreased. That is, a sharper electron beam results. Experiments have shown that in view of the sharper electron beam, the spacing between adjacent spades may, therefore, be decreased without the beam impinging on two spades at one time. This results in a more compact tube.

These and other objects and advantages of the present invention will be better understood from the following detailed description when taken in connection with the accompanying drawings:

Fig. 1 is an isometric view, partly in section, of a magnetron type multiple position beam switching tube which is suitable for use with the present invention;

Fig. 2 is a schematic view of a feedback circuit utilized with a tube of the type shown in Fig. 1 and in accordance with the present invention;

Fig. 3 is a sectional view of a magnetron type beam switching tube having internal feedback electrode means in accordance with the present invention and a schematic diagram for the operation of same;

Fig. 4 shows a sectional view of a beam switching tube and circuit in which the feedback arrangement in accordance with the present invention may be either internal or external of the tube;

Fig. 5 is a simplified diagrammatic view of an alternative external feedback arrangement in accordance with the present invention; and

Fig. 6 is a schematic view of the external feedback arrangement of Fig. 5 applied to a beam switching tube of the type shown in Fig. 1.

Referring to Figs. 1 and 2, there is shown a magnetron type multiple position beam switching tube 10 having within an envelope 1.2 a centrally disposed thermionic cathode 14. The tube It is one of the types disclosed and claimed in the Fan-Kuchinsky patent previously referred to. The cathode 14 is shown as being of the indirectly heated type, but other type cathodes may be used. Surrounding the cathode 14 is an array of spade electrodes 16. Each of the spades are identical, and are coextensive in length with the electron emissive portion of the cathode 14. Each spade 16 is of a generally U shaped transverse cross sectional configuration and is usually constructed of a non-magnetic material in order that the magnetic field, provided by the magnet 11, which permeates the tube 10 is not affected. Each of the spades 16 is insulated from the others, but is connected to a source of positive potential 40 through an individual spade resistor 30.

The base 18 of each spade 16 faces generally inwardly towards the centrally disposed cathode 14 and the sides of the spades extend outwardly.

An array of individual target electrodes 24 surrounds the array of spades 16. Each of the targets is aligned with and disposed opposite the space between two adjacent spades 16 on the side thereof which is more remote from the cathode 14. The individual target electrodes 2- are, as shown in Fig. 2, each connected to a source of positive potential 26 through its own target resistor 28.

An array of individual rod-like beam switching electrodes or grids 36 is positioned between the spades 16 and the target electrodes 24. One of the grids 36 is positioned generally between the lagging edge of each spade I6 and a target electrode 24-. In the illustrated embodiments of this invention the polarity of the magnetic field is such that the electron beam rotates in a clockwise direction.

Alternate ones of the switching grids 36 are connected to the common leads 42, 44, usually within the envelope 12 of the tube, in order to minimize the number of leads which must be brought through the stem of the tube 10. Usually the switching grids 36 are biased at a positive potential through a series resistor 46, 48, for example, which is connected between one of the common leads 42, 44, and a source of potential 50, 52.

As thus far described, the circuit of the tube is norma That is, the spade-cathode potential is such with respect to the surrounding magnetic field that if one of the spades 16 is lowered to, or near to, the cathode potential an electron beam will be formed and will lock in on the leading edge of that spade electrode 16 which is at the lowered potential. Part of the electron beam passes through the spade resistor 30, producing a voltage drop which maintains the spade 16 at or near the cathode potential and locking in the beam automatically. It is assumed that the ohmic value of the spade resistors have the proper value to produce the required voltage drop thereacross. Part of the electron beam also impinges on the output target electrode 24, and the output signal for that beam position is developed across the target resistor 28. The electron beam is caused to switch from one beam position to another by the application of a negative signal to the one of the switching terminals 54, 56 which is conductively connected to the switching grid which is adjacent to the beam position where the electron beam is locked in.

When the potential of the switching grid 36 which is adjacent to the electron beam is lowered sufficiently, the electron beam fans out and a part of it impinges on the next advanced spade. When the electron beam impinges on the advanced spade, an IR drop is produced across the spade load resistor of that spade. When the IR drop exceeds a critical value, the electron beam switches and locks in on the advance spade. Because the next switching grid 36 is still biased at its positive potential, it does not cause the beam to fan out and switch to a further beam position. The individual spade electrodes 16 are each connected to a source of positive potential 40 through a spade impedance element shown as a resistor. The leads (not shown) to the cathode 14, spades 16, target electrodes 24, and switching grids 36 are brought out to the base 32 of the tube to the pins 34.

As previously mentioned, the number of spades 16 which may be disposed about the cathode 14 in an array of a given diameter is limited. Apparently as the physical size of a spade 16 becomes smaller and smaller the effect of the change in the electrostatic field caused by lowering the potential of a single spade is insufiicient to cause an electron beam to be formed between the cathode 14 and the single spade which is at a lowered potential.

Experimental results tend to substantiate the above, since an electron beam was formed in experimental tubes when two adjacent spades of small size were lowered to near to the potential of the cathode, while a beam would not form when the potential on only a single spade was lowered. Further, the beam would switch to an advance spade, during which time both the preceding spade and the advance spade were both at lowered potentials due to the fact that the electron beam was impinging on both the spade at which the beam was locked in and on the advanced spade. However, once the beam switched to the advanced spade and no longer impinged on the preceding. spade, the electron beam became extinguished. Further, when the preceding spade and the advanced spade were grounded the beam re-formed and locked in on the so called advanced spade to which it had previously switched.

Therefore, in accordance with the present invention as shown in Fig. 2, each of the target electrodes 24 is coupled through a diode 58 to the spade of the next preceding beam position. Because of the low forward resistance of the diodes 58, the beam current of each target electrode is divided between its target resistor 28 and the spade resistor 30 of the spade of the preceding beam position. Thus, as the target potential drops when the electron beam switches to a new beam position a portion of the output current is fed back through the diode 58 to the preceding spade and maintains that spade at a lowered potential due to the voltage drop across its spade resistor 30. Thus both the spade 16 on which the electron beam is locked in and the preceding spade are maintained at a lowered potential. The voltage of the preceding spade is determined by the target voltage at the beam position where the electron beam is locked in, but the target potential in many tubes may be lowered to, or near to, the cathode potential without adversely affecting the beam holding and switching functions of the tube.

It should be noted that from the time the electron beam switches from its locked in position at the leading edge of one spade until it is locked in on the leading edge of the advanced spade and impinges on the target electrode associated with the last mentioned spade there is no means for maintaining the former spade at a lowered potential. It might appear, therefore, that the electron beam would become extinguished, because for an instant there was no means to lower the potential of the preceding spade. Actually, the transfer of the electron beam is so rapid that the preceding spade potential does not rise above the critical potential due to the time required to charge the capacity represented by interelectrode capac-itances of the tube and by lead and other circuit capacitances through the spade impedance 30. Thus, before the spade potential on the preceding spade rises to the point where the electron beam might be extinguished as a result thereof, the electron beam impinges on the output electrode of the advanced beam position and the feedback of electrons to the circuit of the preceding spade assures that the preceding spade will be maintained at a lowered potential.

While the immediate object of the feedback arrangement is to increase the possible number of beam positions per unit tube diameter, other beneficial results accrue to the feedback arrangement. The beam current in the tube is increased when two (or even more) previous spades are maintained at a lowered potential, particularly when the preceding spades are maintained at or close to the cathode potential. Thus, the part of the output current which is sacrificed through the feedback arrangement is often more than compensated for by the increase in the overall beam current which permits increased power output.

Further, the increasing of the beam current results in an increase in spade current. This permits the use of spade resistors 30 having a smaller ohmic value, yet still producing a sufficient voltage drop thereacross to lock in the electron beam. Since the beam switching time depends on the R-C constant of the spade circuit, decreasing the R means an increase in the beam switching rate. Since the spade current may be increased as much as five times, or even more, the decrease in switching time is large.

The arrangement shown in Fig. 2 is satisfactory for many uses, but if increasing the beam switching rate is of prime importance, other arrangements, such as shown in Figs. 3 and 4, involving internal feedback within the tube, also serve to minimize the capacity of the spade circuit.

The tube 10a shown in Fig. 3 has an array of rod-like feedback electrodes 60 disposed between the spades 16 and the target electrodes 24. One of the rod-like feedback electrodes 64) is disposed between the leading edge of each spade 16, and the target 24 associated with that beam position. When the electron beam locks in at the leading edge of a spade, part of the electron beam will impinge on the feedback electrode 60 and on the output electrode 24. Each of the feedback electrodes 66 is insulated from the others and is conductively connected to the spade 16 of the preceding beam position through the lead 62. With this feedback arrangement, each tube a will function as a feedback evice only if the electron beam rotates in a single direction. In event it is desired to maintain the preceding spade at a potential other than the potential of the feedback electrode 60, the conductor 62 may be a resistor. it will be recalled, however, that the direction of rotation depends on the polarity of the magnetic field which permeates the tube. The electron flow to the feedback electrode 64 has been found to be suflicient to drop the potential of the preceding spade to, or near to, the potential of the cathode 14. Because the beam current increases when the preceding spade potential is lowered, the insertion of the feedback electrodes 6t) in the path of the electron beam and the splitting up of the output current between the target electrode 24 and the feedback electrode 6t? does not result in any critical lowering of the output current for most applications.

'ln order to reduce the number of leads brought out through the stem of the tube 10a, the connection between each feedback electrode at} and its spade 16 is made with the lead 62 within the tube. This arrangement also permits the spade resistors to be included within the tube envelope, further reducing lead capacitances and permitting higher beam switching speeds as mentioned previously. The beam advancing means including the switching grid circuitry may be the same as in Fig. 2.

in the tube Ttfib shown in Fig. 4 the target electrode of each beam position is conductively connected to the spade of the next preceding beam position. This connection, shown as the lead 66, may either be made within the tube or external thereto. Since a target and a spade are connected together in the arrangement shown in Fig. 4, a single load impedance, indicated by the resistor 68, is provided. If desired, an output signal may be taken from the terminal which is conductively connected between the load impedance 68 and the target 24 and spade 16 associated with that impedance. Since in some tubes, such as a decade counter tube, only one output is required, internal load resistors 68 may conveniently be used. The entire tube and circuit of Fig. 4 except the input means and power supply could be contained in one compact tube envelope. The above statement holds also with tubes having means for taking an output signal from each of the beam positions.

Figure 5 is a simplified view of the feedback arrangement shown in Fig. 6. None of the target, switching grid, or spade leads are shown except those which are directly concerned with the feedback circuit arrangement between two adjacent beam positions of a beam switching tube. The target impedance of target 24a is con nected betwen the target 24a and a source of positive potential and two series connected resistors 74, 76 connected between the tar et 24a and a source of negative potential. The junction between resistors 74, 76 is connected to the cathode 78 of an electron tube 86 A control grid 82 of the tube is biased by the battery 88 so that the tube 80 is cut off except when the electron beam of the beam switching tube impinges on the target 24a. The anode 8d of the tube 80 is connected to the spade 16b, and the resistor 86, connected between the spade 16b and a source of positive potential, serves both as the spade load impedance and the load impedance of the tube 88. For the sake of simplicity it will be assumed that each of the resistors 72, 74, and 76 of the target (24a) circuit have equal ohmic value and the source of positive potential is 200 volts and the source of negative potential is negative volts. Accordingly, the static potential of the anode would be 100 volts positive while the potential of the cathode 78 of the tube 80 would be zero. As mentioned previously, the tube 80 is biassed to cutoff by the battery 38 and thus no current flows through the load impedance 86 except when the electron beam of the beam switching tube is locked in on the spade 16b. When the electron beam of the beam switching tube is locked in on the spade 16a, however, part of the beam impinges on the target 24a, causing the potential of the target to drop. When this occurs the cathode 78 of the tube 81') becomes charged negatively with respect to the grid 82, causing conduction through the tube 8?- and dropping the potential of the spade 16b due to the voltage drop across the load resistor 86.

By choosing the values of the resistors 72, 74-, and 76 as well as the value of the resistor 36 and the power supply potentials, the potential of the spade 1611 may be controlled accurately to any predetermined level. The tube at may have characteristics such that a small change in bias causes the tube to conduct in a full on manner. Thus the beam switching tube may be modulated over a fairly wide range without affecting the potential of the preceding spade 16b.

The full feedback circuit of Fig. 5 is shown in Fig. 6. Connections to the switching grids 36 are as shown in Fig. 2 except that a common battery d0 replaces the batteries 5t 52 which were indicated as potential sources in Fig. 2. The function of the feedback circuit is the same as explained in connection with Fig. 5. In practice the tubes 8t,- would probably be five dual triodes. Normally each of the tubes 89 would be connected in an identical manner.

Thus, it can be seen that the present invention provides a convenient, economical and reliable means for enlarging the number of beam positions which are permissible in a beam switching tube of given diameter, providing a faster beam switching rate in such tubes and of increasing the power output capabilities of such tubes.

We claim:

1. A magnetron type beam switching tube comprising a thermionic cathode and adapted to receive a magnetic field parallel to the cathode, a plurality of individual spade electrodes, said spade electrodes being disposed about said cathode in a hollow cylindrical array, a plurality of electron receiving target electrodes, said target electrodes being disposed about said cathode in a hollow cylindrical array of larger diameter than said array of spades, said target array being concentric and coaxial with respect to said array of spades, each of said target electrodes being disposed in axial alignment with the space between two adjacent spade electrodes, each of said target electrodes being conductively connected to a spade electrode which is adjacent to the spade electrodes defining the space with which the target electrode is aligned in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the common electrodes to lower the spade potential in response to current flow from either the connected electrode or the spade.

2. A magnetron type beam switching tube comprising a thermionic cathode and adapted to receive a magnetic field parallel to the cathode, a plurality of individual spade electrodes, said spade electrodes being disposed about said cathode in a hollow cylindrical array, a plurality of electron receiving target electrodes, said target electrodes being disposed about said cathode in a hollow cylindrical array of larger diameter than said array of spades, said target array being concentric and coaxial with respect to said array of spades, each of said target electrodes being disposed in axial alignment with the space between two adjacent spade electrodes, each of said target electrodes being conductively connected to a spade electrode which is adjacent to the spade electrodes defining the space with which the target electrode is aligned in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an array of rod-like electrodes, each of said rod-like electrodes being disposed between one of said spade electrodes and one of said target electrodes.

3. A magnetron type beam switching tube comprising a thermionic cathode and adapted to receive a magnetic field parallel to the cathode, a plurality of individual spade electrodes, said spade electrodes being disposed about said cathode in a hollow cylindrical array, a plurality of electron receiving target electrodes, said target electrodes being disposed about said cathode in a hollow cylindrical array of larger diameter than said array of spades, said target array being concentric and coaxial with respect to said array of spades, each of said target electrodes being disposed in axial alignment with the space between two adjacent spade electrodes, at least one of said target electrodes being conductively connected to a spade electrode which is adjacent to the spade electrodes defining the space with which the target electrode is aligned in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the conductively connected electrodes to lower the spade potential in response to current flow from either the connected target electrode or the spade electrode.

4. A magnetron type beam switching tube comprising, within an evacuated envelope, a tubular indirectly heated thermionic cathode, the tube being adapted to receive a magnetic field parallel to the cathode, a plurality of individual spade electrodes, each being insulated from the others and each having a curved transverse cross sectional configuration, said spade electrodes being disposed about said cathode in a hollow cylindrical array, a plurality of electron receiving target electrodes, each of which is insulated from the others, said target electrodes being disposed about said cathode in a hollow cylindrical array of larger diameter than said array of spades, said target array being concentric and coaxial with said array of spades, each of said target electrodes being disposed in axial alignment with the space between two adjacent spade electrodes, each of said target electrodes being conductively connected within said tube to a spade electrode which is adjacent to the spade electrodes defining the space with which the target electrode is aligned in the direction opposite to that in which the beam tends to totate under influence of said magnetic field, and an impedance device coupled from the conductively connected electrodes to lower the spade potential in response to current flow from either the connected target electrode or the spade electrode.

5. A magnetron type beam switching tube comprising, within an evacuated envelope, a tubular indirectly heated thermionic cathode, a plurality of individual spade electrodes each being insulated from the others and each having a substantially U shaped cross sectional configuration, said spade electrodes being disposed about said cathode in a hollow cylindrical array, a plurality of electron receiving target electrodes each of which is insulated from the others, said target electrodes being disposed about said cathode in a hollow cylindrical array of larger diameter than said array of spades, said target array being concentric and coaxial with said array of spades, each of said target electrodes being disposed in axial alignment with the space between two adjacent spade electrodes, each of said target electrodes being conductively connected to a spade electrode which is adjacent to the spade electrodes defining the space with which the target electrode is aligned, an array of beam switching electrodes, one of said beam switching electrodes being disposed adjacent to each spade electrode, and means external to said tube envelope for providing a magnetic field which permeates said tube, the flux lines of said field which are in the spade-cathode space being generally parallel to the longitudinal axis of said cathode, the said beam forming electrode connected to the target electrode being that electrode in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field.

6. A magnetron type beam switching tube comprising, within an hermetically sealed envelope, an elongated thermionic cathode, means external to said tube envelope for providing a magnetic field which permeates said tube,

the flux lines of said field which are in the spade-cathode space being generally parallel to the longitudinal axis of said cathode and tending to rotate the electron beam issuing from the cathode in one direction about the axis of the cathode, an array of beam forming and directing electrodes and two arrays of electron receiving target elec trodes, each of said arrays being coaxial and concentric with respect to said cathode, a target electrode of each array of target electrodes being disposed beyond said array of beam forming and directing electrodes and aligned with the space between two adjacent beam forming and directing electrodes, one of each pair of target electrodes which are so disposed being conductively connected to a beam forming and directing electrode which is adjacent to the beam forming and directing electrodes defining the space with respect to which said target electrodes are aligned in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the conductively connected electrodes to lower the beam forming electrode potential in response to current flow from either the connected target electrode or the beam forming electrode.

7. A magnetron type beam'switching tube comprising, within an hermetically sealed envelope, an elongated thermionic cathode, means external to said tube envelope for providing a magnetic field which permeates said tube, the flux lines of said field which are in the spade cathode space being generally parallel to the longitudinal axis of said cathode, an array of beam forming and directing electrodes and at least one array of electron receiving target electrodes, each of said arrays being coaxial and concentric with respect to said cathode, a target electrode of the array of target electrodes being aligned with the space between two adjacent beam forming and directing electrodes, each target electrode which is so disposed being conductively connected to a beam forming and directing electrode which is adjacent to the beam forming and directing electrodes defining the space with respect to which said target electrodes are aligned in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the conductively connected electrodes to lower the beam forming electrode potential in response to current flow from either the connected target electrode or the beam forming electrode.

8. A magnetron type beam switching tube comprising, within an hermetically sealed envelope, an elongated thermionic cathode, means external to said tube envelope for providing a magnetic field which permeates said tube, the flux lines of said field which are in the spade-cathode space being generally parallel to the longitudinal axis of said cathode, an array of beam forming and directing electrodes and two arrays of electron receiving target electrodes, each of said arrays-being coaxial and concentric with respect to said cathode, a target electrode of each array of target electrodes aligned with the space between two adjacent beam forming and directing electrodes, one of each pair of target electrodes which are so disposed being conductively connected to a beam forming and directing electrode which is adjacent to the beam forming and directing electrodes defining the space with respect to which said target electrodes are aligned in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, an impedance device coupled from the conductively connected electrodes to lower the beam forming electrode potential in response to current flow from either the connected target electrode or the beam forming electrode, and an array of beam switching electrodes, one of said beam switching electrodes being disposed adjacent to each beam forming and directing electrodes.

9. A magnetron type beam switching tube comprising, within an hermetically sealed envelope, an elongated thermionic cathode, an array of substantially trough shaped beam forming and directing electrodes and two arrays of electron receiving target electrodes, the' target electrodes of one array being rod-like in form, each of said arrays being coaxial and concentric with respect to said cathode, a target electrode of each array of target electrodes being disposed beyond said array of beam forming and directing electrodes and aligned with the space between two adjacent beam forming and directing electrodes, one of each pair of target electrodes which are so disposed being conductively connected to a beam forming and directing electrode which is adjacent to the beam forming and directing electrodes defining the space with respect to which said target electrodes are aligned an impedance device coupled from the conductively connected electrodes to lower the beam forming electrode potential in response to current flow from either the connected target electrode or the beam forming electrode, and an array of rod-like beam switching electrodes, each of said beam switching electrodes being disposed adjacent to a separate beam forming and directing electrode, and magnetic field means external to said tube for providing fiux lines within said tube which are substantially parallel to the longitudinal axis of the cathode, the said beam forming electrode connected to the target electrode being that electrode in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field.

10. Beam switching apparatus comprising a magnetron type beam switching tube having a thermionic cathode and adapted to receive a magnetic field parallel to the,

cathode, an array of spade electrodes surrounding said cathode, and an array of target electrodes, said target electrodes being equal in number to said spade electrodes, each of said target electrodes being disposed in alignment with the space between two adjoining spade electrodes, means for coupling energy from each target electrode to a spade electrode which is adjacent to the adjoining spades with which the target electrode is associated in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the coupled electrodes to lower the spade potential in response to energy from either the target electrode or the coupled spade electrode.

11. Beam switching apparatus comprising a magnetron type beam switching tube having a thermionic cathode and adapted to receive a magnetic field parallel to the cathode, an array of spade electrodes surrounding said cathode, and an array of target electrodes, said target electrodes being equal in number to said spade electrodes, each of said target electrodes being disposed in a1ignment with the space between two adjoining spade electrodes, means for unidirectionally coupling electrical energy from each target electrode to a spade electrode which is adjacent to the adjoining spades with which the target electrode is associated in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the coupled electrodes to lower the spade potential in response to current flow from either the target electrode or the coupled spade electrode.

12. Beam switching apparatus in accordance with claim 11, wherein said means for unidirectionally couplin g electrical energy includes a diode.

13. Beam switching apparatus comprising a magnetron type beam switching tube having a thermionic cathode and adapted to receive a magnetic field parallel to the cathode surface, an array of spade electrodes surrounding said cathode, and an array of beam receiving electrodes, said beam receiving electrodes being equal in number to said spade electrodes, each of said beam receiving electrodes being disposed in alignment with the space between two adjoining spade electrodes, means for coupling energy from each beam receiving electrode to a spade electrode which is adjacent to the adjoining spades with which the beam receiving electrode is associated in the direction opposite to that in which the beam tends to rotate under influence of said magnetic field, and an impedance device coupled from the coupled electrodes to lower the spade potential in response to current flow from either the coupled beam receiving electrode or the spade electrode.

References Cited in the file of this patent UNiTED STATES PATENTS 2,223,001 Farnsworth Nov. 26, 1940 2,278,630 Winter Apr. 7, 1942 2,591,997 Backmark Apr. 8, 1952 2,599,949 Skellett June 10, 1952 2,620,454 Skellett Dec. 2, 1952 

